Sense amplifiers are used for reading stored data from memory arrays. The stored data in a memory array may be provided to a data line, which is connected to a sense amplifier. The sense amplifier then amplifies the data.
Sense amplifiers include single-ended amplifiers and differential sense amplifiers. In the single-ended sense amplifiers, the data retrieved from the memory array are amplified directly, for example, through an inverter. The single-ended sense amplifiers require the signals read from the memory array to have high swings, and are not reliable for small-signal sensing. Furthermore, the access time of the single-ended sense amplifiers is long, and the read margins of the single-ended sense amplifiers are low. Therefore, although the single-ended sense amplifiers typically have simple designs that require small chip areas, the performance of the single-ended sense amplifiers is not satisfactory.
In a differential sense amplifier, a reference voltage generator may be needed to generate a reference voltage. A reference memory column may also be needed to provide a signal to the reference voltage generator. The data read from the memory array may be provided to the differential sense amplifier, which receive the data and the reference voltage as differential input signals. The state of the differential sense amplifier is determined by the voltage levels of the reference voltage and the data.
In general, with the design of the reference memory columns, differential sense amplifiers may reliably sense and amplify the data. However, the reference memory column and the reference voltage generator require complex circuit designs to ensure that the reference voltage is stable. Accordingly, a significant chip area penalty is involved.